The environmental law organisation said the plans still fell far short of what was needed to bring air pollution to within legal limits as soon as possible.

ClientEarth CEO James Thornton said: “The UK Government’s stubborn failure to tackle illegal and harmful levels of pollution in this country means that we have no choice but to take legal action. We need clarity from the government and for that we’ve been forced to go back to court.”

The latest plan backtracks on previous commitments to order 5 cities to introduce clean air zones by 2020;

The plan does not require any action in 45 local authorities in England, despite them having illegal levels of air pollution.

The plan does not require any action by Wales to bring down air pollution as quickly as possible.

ClientEarth understands that Leicester City Council, as well as Oxford City Council have written to the government raising doubts about the plans. These include claims that the government has seriously underestimated pollution levels in their cities and excluded them from access to essential support to fight the problem.

Illegal air pollution

The UK has had illegal levels of nitrogen dioxide, which in towns and cities comes mostly from diesel vehicles, since legal limits came into effect in 2010. In order to avoid any further delay to ongoing work by Defra, DfT and local authorities, ClientEarth is not calling for the current plan to be overturned, but instead to be supplemented.

ClientEarth names the Secretary of State for the Environment, Food and Rural Affairs, the Transport Secretary and the Cabinet Secretary for Environment and Rural Affairs in the Welsh Government as defendants.

Thornton added: “This is a national problem that requires a national solution. The government’s own evidence shows that we need a national network of charging clean air zones, which will keep the dirtiest vehicles out of the most polluted areas of our towns and cities, so why aren’t drivers being prepared for it? It’s time ministers came clean about the size of the problem and the difficult decisions needed to solve it.”

“The government should be helping people and small businesses move to cleaner forms of transport. We need fiscal policies to drive a shift away from dirty diesel, so November’s Budget will be a litmus test of the government’s resolve. The car industry helped get us into this mess so they should be helping get us out of it by contributing to a clean air fund, as they have done in Germany.”

In Germany, the government recently secured €250million from the car industry towards a fund to help German cities – where ClientEarth has been involved in a number of legal challenges – to reduce pollution. ClientEarth thinks the car industry must be part of the solution, having helped create the problem of illegal air pollution in our towns and cities in the first place.

As part of its Poisoned Playgrounds campaign, ClientEarth recently revealed that there are more than 950 schools in the UK on or near illegally polluted roads.

Latest legal challenge

ClientEarth has won two cases against the UK Government over illegal levels of air pollution in the UK.

In April 2015 the Supreme Court ordered the government to produce new air quality plans which demonstrated how it would bring air pollution down to legal levels as soon as possible.

In November 2016 the High Court declared the resulting plans illegal and ordered new ones, which were produced in July this year. It is these latest plans that ClientEarth is challenging with this latest legal action.